Tuning Fork Research Articles

Design and Fabrication of Quartz MEMS Based Double-ended Tuning Fork Resonator

This paper presents the design and fabrication of double-ended tuning fork (DETF) resonator based on quartz. DETF resonator was designed with two tines structure, due to this configuration has the advantage of providing dynamic balance. Both surface and side electrode were designed on DETF tines in order to enhance the piezoelectric effect. DETF resonator was fabricated from a quartz substrate by chemical wet etching and photolithography processes, the key feature of fabrication is to create Cr/Au metal films, which should be strong enough to withstand the aggressive quartz etchant, meanwhile, the wet etching parameters was optimized in order to reduce the sidewall structure in +X orientation which can greatly deteriorate vibrating characteristics of DETF tines. Experimental results demonstrated that the Q value would be lowered and motional resistance be increased with the force sensitivity increase of DETF tines.

Quartz-enhanced multiheterodyne resonant photoacoustic spectroscopy

The extension of dual-comb spectroscopy (DCS) to all wavelengths of light along with its ability to provide ultra-large dynamic range and ultra-high spectral resolution, renders it extremely useful for a diverse array of applications in physics, chemistry, atmospheric science, space science, as well as medical applications. In this work, we report on an innovative technique of quartz-enhanced multiheterodyne resonant photoacoustic spectroscopy (QEMR-PAS), in which the beat frequency response from a dual comb is frequency down-converted into the audio frequency domain. In this way, gas molecules act as an optical-acoustic converter through the photoacoustic effect, generating heterodyne sound waves. Unlike conventional DCS, where the light wave is detected by a wavelength-dependent photoreceiver, QEMR-PAS employs a quartz tuning fork (QTF) as a high-Q sound transducer and works in conjunction with a phase-sensitive detector to extract the resonant sound component from the multiple heterodyne acoustic tones, resulting in a straightforward and low-cost hardware configuration. This novel QEMR-PAS technique enables wavelength-independent DCS detection for gas sensing, providing an unprecedented dynamic range of 63 dB, a remarkable spectral resolution of 43 MHz (or ~0.3 pm), and a prominent noise equivalent absorption of 5.99 × 10-6 cm-1·Hz-1/2.

Compact Viscosity Sensors for Downhole Enhanced Oil Recovery Polymer Fluid Degradation Monitoring

Summary There are currently no technologies available to measure polymer solution viscosities at realistic downhole conditions in a well during enhanced oil recovery (EOR). In this paper, custom-made probes using quartz tuning fork (QTF) resonators are demonstrated for measurements of viscosity of polymer fluids in the laboratory. The electromechanical response of the resonators was calibrated in simple Newtonian fluids and in non-Newtonian polymer fluids at different concentrations. The responses were then used to measure field-collected samples of polymer injection fluids. In the polymer fluids, the measured viscosity values by tuning forks were lower than those measured by the conventional rheometer at 6.8 s−1, closer to the solvent viscosity values. However, the predicted rheometer viscosity vs. QTF-measured viscosity showed a distinct exponential correlation (R2=0.9997), allowing for an empirical calibration between the two viscometers for fluids having the same solvent and polymer compositions. The QTF sensors produced acceptable viscosity measurements of polymer fluids within the required polymer concentration ranges used in the field and predicted field sample viscosities with less than 1–2 cp (or 10–20%) error from the rheometer data. Results were validated based on separate independent tests where the devices were used to measure the viscosity of Newtonian fluids and non-Newtonian polymer fluids in a series of consecutive dip tests, simulating more realistic usage. These devices can be used to measure either the “relative” viscosity changes from a polymer solution prior and post-injection or to measure a “calibrated” viscosity via empirical exponential correlation. The compact QTF sensors developed in this study can be easily integrated into portable systems for laboratory or wellsite deployment as well as logging tools for downhole deployment. This work also demonstrates the ability of these QTF devices to make sensitive viscosity measurements at high-frequencies, opening opportunities for their use in high-frequency rheology studies of EOR fluids.

Approach to Sudden Hearing Loss Among Primary Care Physicians in Riyadh, Saudi Arabia.

A medical emergencyknown as sudden sensorineural hearing loss (SSNHL)affects the ears suddenly, has a considerable probability of negative cognitive and functional outcomes, and can influence the patient's quality of life. Primary care physicians play a crucial role in diagnosing SSNHL and initiating prompt and efficient management since they are the ones who would likely encounter it initially. This study aims to evaluate the present knowledge, diagnostic, and management perspective of SSNHL among primary care physicians in Riyadh, Saudi Arabia. A self-generated questionnaire with 17 questions was developed, and a link to the online survey was delivered to primary care physicians (PHPs) in Riyadh, SaudiArabia, concerning the management of SSNHL. The knowledge level regarding SSNHL was evaluated, in which 21 (25%) of the participants had a low knowledge level, 34 (40.5%) had moderate knowledge, and 29 (34.5%) had a high knowledge level. Among 84 participants, 20 (23.8%) were confident in their ability to administer and understand the findings of tuning fork tests (TFT) to differentiate between sensorineural hearing loss and conductive hearing loss, whereas 64 (76.2%) were unsure about it. In addition, to distinguish between sensorineural hearing loss and conductive hearing loss, 62 (73.8%) participants were confident, and 22 (26.2%) participants were skeptical about their ability to interpret a formal audiogram. Considering SSNHL as a medical emergency, in our survey, many family doctors would make proper referral and treatment decisions. However, TFTs were underutilized for guiding management decisions compared to other ways to distinguish between conductive and sensorineural hearing loss.

Highly sensitive and reversible MXene-based micro quartz tuning fork gas sensors with tunable selectivity

Due to their distinctive morphology, significant surface-to-volume ratio, and metal-like electrical conductivity, MXenes have emerged as highly promising gas-sensing materials. Traditional MXene-based gas sensors predominantly rely on the electrical conductivity of MXenes for signal transduction. However, it is crucial to explore alternative signal transduction mechanisms to fully unlock the potential of MXenes in gas sensing applications. In this study, we have successfully showcased the development of a mass-transduction-based MXene gas sensor, utilizing MXenes as the adaptable receptor and MQTF as the transducer. The interaction between the gas analyte and MXenes induces a change in mass, resulting in a resonant frequency shift of the MQTF. This signal transduction mechanism eliminates the dependency on the electrical conductivity of MXenes, offering a broader range of possibilities for chemical modification of MXenes without concerns about compromising their conductivity. By engineering Ti3C2Tx surfaces, we have demonstrated high sensitivity and selectivity tuning of MXene-MQTF gas sensors for detecting CO, SO2, and NH3. This antisymmetric mass-transduction-based (low-cost, stable, sensitive, and practical tuning fork-based) MXene gas sensor demonstrated exceptional sensing performance, customizable selectivity, and high cost-effectiveness. This study paves the way for designing high-performance MXene-based chemical sensors and expands the scope of potential applications in air quality monitoring, wearable devices, the Internet of Things (IoT), and robotics.

Influence of the Gain–Bandwidth of the Front-End Amplifier on the Performance of a QEPAS Sensor

The quartz tuning fork used as an acoustic sensor in quartz-enhanced photo-acoustic spectroscopy gas detection systems is usually read out by means of a transimpedance preamplifier based on a low-noise operational amplifier closed in a feedback loop. The gain–bandwidth product of the operational amplifier used in the circuit is a key parameter which must be properly chosen to guarantee that the circuit works as expected. Here, we demonstrate that if the value of this parameter is not sufficiently large, the response of the preamplifier exhibits a peak at a frequency which does not coincide with the series resonant frequency of the quartz tuning fork. If this peak frequency is selected for modulating the laser bias current and is also used as the reference frequency of the lock-in amplifier, a penalty results in terms of signal-to-noise ratio at the output of the QEPAS sensor. This worsens the performance of the gas sensing system in terms of ultimate detection limits. We show that this happens when the front-end preamplifier of the quartz tuning fork is based on some amplifier models that are typically used for such application, both when the integration time of the lock-in amplifier filter is long, to boost noise rejection, and when it is short, in order to comply with a relevant measurement rate.

Lord Rayleigh versus Chladni and KFC Sanders: Who is correct about tuning forks?

The tuning fork is one of my favorite pieces of acoustical apparatus (as evidenced by three published papers in the American Journal of Physics and an article in Acoustics Today). A favorite problem (formerly used on final exams, and currently used as a hands-on activity) for the first-year graduate structural vibrations course I teach, requires students to read excerpts from four textbooks which make a statement about the boundary conditions for the tines of a tuning fork. Lord Rayleigh and Barton describe a tuning fork as two fixed-free bars joined at the base, while Chladni and Kinsler, Frey, Coppens, and Sanders describe a tuning fork as free-free bar bent into a U- shape. Who is correct? Students are required to measure the frequency spectrum of a tuning fork and match the resulting frequency ratios to what they would obtain by solving the boundary condition problem by treating the fork tines as a free-free or fixed-free bar undergoing flexural vibrations. This talk will work through the problem and will illustrate some of the pitfalls that often trip up students. And yes, the question of who is correct will be answered!

Design, fabrication, and characterization of a high-sensitivity integrated quartz vibrating beam accelerometer.

This paper describes the design, fabrication, and characterization of a quartz vibrating beam accelerometer consisting of a metal spring-mass and quartz double-ended tuning forks (DETFs). In this approach, the inertial force of the proof mass pulls or compresses the DETFs, affecting their resonance frequency and, thus, enabling the quasi-digital measurement of acceleration. An isolation structure was specifically designed to prevent the external interference stress from transforming into the DETFs and to decrease the DETFs' thermal stress as the ambient temperature changes. A stress-free and high-precision wire-cut electrical discharge machining process was introduced to solve the fabrication problem of flexible hinges, and a femtosecond laser was used to release the proof mass, comprehensively considering the compatibility of the fabrication process and structural design. The oscillation excitation and detection of the DETFs were analyzed, and the DETFs were fabricated using a micro-electromechanical systems process. Sensor dimensions were optimized to improve sensor sensitivity. An accelerometer prototype was fabricated, and its performance was characterized. The tested scale factor was 157.28 Hz/g, and its stability was 16.54 ppm. The bias stability and 1g stability at 1h were 18 and 7.84 µg, respectively. The experimental results validated the feasibility of the sensor design.

Experimental Investigation of Mode Localization's Bifurcation Topology Transfer in Electrostatically Coupled Tuning Fork Resonators.

Bifurcation topology transfer phenomena in the presence of mode localization are investigated using double-ended fixed electrostatically coupled tuning fork resonators. An analytical model is proposed for the coupled tuning fork resonators, and the effects of feedthrough capacitance on the structure are also analyzed and eliminated by means of data post-processing. Then, an open-loop experimental platform is established, when the system is in balance state, the quality factor is obtained under test as Q = 9858, and comparison of the experiment with numerical simulation results is in good agreement. Finally, with the voltage increases, the two resonators gradually exhibit nonlinear characteristics. It is worth noting that when one of the coupled resonators exhibits nonlinear vibration behavior, even though the vibration amplitude of the other resonator is lower than the critical amplitude, it still exhibits nonlinear behavior, and the results confirm the existence of the bifurcation topology transfer phenomenon in coupled resonators' mode localization phenomenon.

How Urban-Tolerant Are They? Testing Prey–Capture Behavior of Introduced Jorō Spiders (Trichonephila clavata) Next to Busy Roads

An invasive orb-weaving spider from east Asia is now spreading through the southeastern United States; Trichonephila clavata (the “jorō spider”) makes large, imposing webs seemingly everywhere, including in urban landscapes, and even next to busy roads. However, areas near roads come with frequent disturbances, including auditory and vibrational, which for many animals, leads to physiological or behavioral changes. Here we tested if varying levels of road traffic affect the prey–capture behavior of jorō spiders in northeast Georgia. We visited roadsides that ranged in traffic density and exposed nearby jorō spiders to a simulated prey (a tuning fork at 128 hz frequency, touched to the web), and recorded whether or not the spider attacked it. Out of 357 total trials across 20 different roads, jorō spiders attacked the simulated prey 59% of the time, but at the local scale, there was high variability in this rate; at some roadsides, over 80% of the spiders attacked, while at others, less than 30% did. When all roads were considered collectively, there was a small but significant (negative) correlation between daily road traffic and spider attack rates. Put another way, spiders near moderate- to heavy-traffic roads were slightly less likely to attack than those near low-traffic roads (51% vs. 65%). Jorō spiders appear to be able to live near roads, but this does come with a cost in terms of prey capture. However, spiders near busier roads did not weigh less than those in other sites, suggesting they may be able to compensate for the disturbance. These findings add to the accumulating evidence around this species that points to its ability to exist in human-dominated landscapes, which will likely aid its spread in the introduced range.

Design and implementation of a temperature-insensitive heterogeneous resonant magnetic field sensor

A heterogeneous resonant magnetic field sensor is developed by using a FeGa plate, a quartz crystal double-ended tuning fork (DETF) resonator and a sapphire crystal plate. The double ends of the DETF are bonded to the ends of the magnetostrictive FeGa thin plate through two spacers, forming a resonant magnetic sensitive element. The C-cut sapphire crystal plate as a temperature compensation layer is bonded to the bottom of the magnetic sensitive element. When the temperature fluctuates, the bending deformation caused by the heterogeneous sensitive structure eliminates the thermal stress caused by the thermal expansion effect, thereby reducing the temperature drift of the sensor. The impact of different thicknesses of the sapphire substrate on reducing temperature drift in the sensor is analysed through theoretical calculation and finite element simulation. A sensor prototype was fabricated with a sapphire substrate thickness of 0.45 mm. The experimental results demonstrate that the temperature coefficient of frequency (TCF) of the sensor is reduced from 8.73 Hz/°C to 0.47 Hz/°C in the 0 °C to 60 °C range, and the sensitivity and resolution in the linear region of the sensor are 5.63 Hz/Oe and 42μOe (4.2nT), respectively.

EXPERIMENT TO DETERMINE THE RELATIONSHIP BETWEEN TEMPERATURE AND TUNING FORK FREQUENCY

A tuning fork is a special tool made of metal and shaped like the letter U with one handle. Tuning forks can produce certain frequencies; usually, the value is written on the handle. This study aims to investigate the relationship between temperature and changes in tuning fork frequency and model it using polynomial regression. This research uses laboratory experiments with tuning forks that have frequencies of 341.3 Hz, 426.5 Hz, and 512 Hz, then the temperature on the tuning fork is varied from 30C to 220C with a difference of 10C. The study's results adjusted R-Square values sequentially 0.94745, 0.99565, and 0.97721, which stated the relationship between temperature and frequency changes. The Adjusted R-Square value close to 1 means that changes in temperature on the tuning fork greatly influence changes in the frequency produced by the tuning fork. The polynomial regression model used is very suitable

Quartz-enhanced photoacoustic spectroscopy sensing using trapezoidal- and round-head quartz tuning forks.

In this Letter, two novel, to the best of our knowledge, quartz tuning forks (QTFs) with trapezoidal-head and round-head were designed and adopted for quartz-enhanced photoacoustic spectroscopy (QEPAS) sensing. Based on finite element analysis, a theoretical simulation model was established to optimize the design of QTF. For performance comparison, a reported T-head QTF and a commercial QTF were also investigated. The designed QTFs have decreased resonant frequency (f0) and increased gap between the two prongs of QTF. The experimentally determined f0 of the T-head QTF, trapezoidal-head QTF, and round-head QTF were 8690.69 Hz, 9471.67 Hz, and 9499.28 Hz, respectively. The corresponding quality (Q) factors were measured as 11,142, 11,411, and 11,874. Compared to the commercial QTF, the resonance frequencies of these QTFs have reduced by 73.45%, 71.07%, and 70.99% while maintaining a comparable Q factor to the commercially mature QTF. Methane (CH4) was chosen as the analyte to verify the QTFs' performance. Compared with the commercial QTF, the signal-to-noise ratio (SNR) of the CH4-QEPAS system based on the T-head QTF, trapezoidal-head QTF, and round-head QTF has been improved by 1.75 times, 2.96 times, and 3.26 times, respectively. The performance of the CH4-QEPAS sensor based on the QTF with the best performance of the round-head QTF was investigated in detail. The results indicated that the CH4-QEPAS sensor based on the round-head QTF exhibited an excellent linear concentration response. Furthermore, a minimum detection limit (MDL) of 0.87 ppm can be achieved when the system's average time was 1200 s.

High-sensitivity methane detection based on QEPAS and H-QEPAS technologies combined with a self-designed 8.7 kHz quartz tuning fork

Methane (CH4) is a greenhouse gas as well as being flammable and explosive. In this manuscript, quartz-enhanced photoacoustic spectroscopy (QEPAS) and heterodyne QEPAS (H-QEPAS) exploring a self-designed quartz tuning fork (QTF) with resonance frequency (f0) of ∼8.7 kHz was utilized to achieve sensitive CH4 detection. Compared with the standard commercial 32.768 kHz QTF, this self-designed QTF with a low f0 and large prong gap has the merits of long energy accumulation time and low optical noise. The strongest line located at 6057.08 cm−1 in the 2v3 overtone band of CH4 was chosen as the target absorption line. A diode laser with a high output power of > 30 mW was utilized as the excitation source. Acoustic micro-resonators (AmRs) were added to the sensor architecture to amplify the intensity of acoustic waves. Compared to the bare QTF, after the addition of AmRs, a signal enhancement of 149-fold and 165-fold were obtained for QEPAS and H-QEPAS systems, respectively. The corresponding minimum detection limits (MDLs) were 711 ppb and 1.06 ppm for QEPAS and H-QEPAS sensors. Furthermore, based on Allan variance analysis the MDLs can be improved to 19 ppb and 27 ppb correspondingly. Compared to the QEPAS sensor, the H-QEPAS sensor shows significantly shorter measurement timeframes, allowing for measuring the gas concentration quickly while simultaneously obtaining f0 of QTF.

Molecularly Imprinted Chitosan Modified Quartz Tuning Fork Sensors for Real Time Biosensing in Liquid Environment

Several new sensing technologies have emerged to meet the escalating demand for accurate and rapid diagnosis. We present an overview of the development of highly sensitive and selective Quartz Tuning Fork (QTF)-based sensors in a liquid environment, which will be critically important for contemporary diagnostic methods reliant on sensing technologies. The purpose of this study is to modify QTF prongs using molecularly imprinted chitosan, in combination with the operation of a quartz tuning fork as a piezoelectric crystal for biomedical applications. Through real-time data acquisition, we evaluate QTF resonance frequency shifts in dry and liquid environments using a model protein, BSA. As a result, the QTF-based sensor fails to detect BSA in dry conditions. It is however possible to measure frequency shifts ranging from 5 to 25 µg /mL within a liquid matrix. There is a rapid equilibration response time of 2 to 10 minutes depending on the concentration of BSA in the sensor. With the developed QTF-based sensor, a sensitivity of 1.1069 Hz/ µg has been achieved within the liquid matrix. As a result of the excellent properties of molecularly imprinted chitosan, it has been possible to develop a QTF-based biosensor capable of acquiring real-time data even when it is in liquid solutions.

Evanescent wave quartz-enhanced photoacoustic spectroscopy employing a side-polished fiber for methane sensing

We present an all-fiber-based laser gas analyzer (LGA) employing quartz-enhanced photoacoustic spectroscopy (QEPAS) and a side-polished fiber (SPF). The LGA comprises a custom quartz tuning fork (QTF) with 0.8 mm prong spacing, two acoustic micro-resonators (mR) located on either side of the prong spacing, and a single-mode fiber containing a 17 mm polished section passing through both mRs and QTF. The SPF polished face is positioned to enable the evanescent wave (EW) to create a photoacoustic wave and excite the fundamental flexural mode of the QTF. Sensor performance was demonstrated using methane in nitrogen gas mixtures, with CH4 mixing ratios ranging from 75 ppmv to 1% (by volume), measured with an accumulation time of 300 ms, and a minimum detection limit of 34 ppmv subsequently determined. The EW-QEPAS sensor is ideal for miniaturization, as it does not contain any free-space optics and is suitable for gas sensing in harsh environments and where mobility is required.

A novel colorimetric tuning fork sensor for ammonia monitoring

In this work, we reported the design and performance of a novel colorimetric tuning fork (CTF)-based gas sensor that could simultaneously capture both chemical and mechanical information of the same sensing event. The CTF sensor could transduce optical signals from a colorimetric reaction and frequency signals from the mass change. By transducing 2-dimensional (2D) sensing signals on the same CTF sensing unit, different aspects of physicochemical properties could provide a rich spectrum of binding events, leading to more accurate, sensitive, and reproducible gas detection. We demonstrated the CTF-based 2D sensing concept by coating bromophenol blue on the prongs of a micro quartz tuning fork (MQTF) as the receptor for ammonia detection. Our test results exhibit CTF ammonia sensor could reversibly detect ammonia in the air over a wide range (500 ppb - 1000 ppm) with a detection limit of 500 ppb and excellent selectivity. Due to its small size (a few millimeters), low cost (less than $1), simple fabrication process, and high performance, the CTF sensor could serve as an excellent chemical sensing unit for wearables and point-of-care screening tools.

Simultaneous dual-harmonic detection for LITES with a multi-pass configuration based on combined flexural modes of a quartz tuning fork

The simultaneous dual-harmonic detection for light-induced thermoelastic spectroscopy (LITES) with a multi-pass configuration based on combined flexural modes of a quartz tuning fork (QTF) is demonstrated. To enhance the photothermal energy absorbed by a custom QTF, the laser beam is designed to pass through the QTF multiple times. With dual-frequency modulation methodology, the second harmonic (2f_fun) signal and the first harmonic (1f_ove) signal are simultaneously inspired at resonant frequencies of fundamental and overtone flexural modes of the QTF, respectively. Thus, precise light intensity and gas concentration can be retrieved concurrently with corresponding 1f and 1f-normalized 2f signals using frequency division multiplexing technology. In comparison to traditional LITES under the same condition sensor, our triple-pass configuration performs 1.84 times better in signal-to-noise ratio (SNR). According to Allan variance analysis, 1f-normalized 2f signal enables a longer integration time of 1100 s and a lower detection limit of 0.07 ppm. The corresponding normalized noise equivalent absorption coefficient (NNEA) is 0.8 × 10−9 cm−1W/Hz1/2.

A laterally sensitive quartz vibrating beam accelerometer for inertial navigation application

To improve the sensitivity and stability of a quartz vibrating beam accelerometer (QVBA), a laterally sensitive structure was developed that utilizes the force-frequency characteristics of a quartz double-ended tuning fork (DETF) to realize quasi-digital measurement of acceleration. Two DETFs were purposely designed for the sidewalls of the proof mass, and the hinge of the spring-mass structure was along the proof-mass thickness, which improved the sensitivity. Laterally sensitive structures can also solve the fabrication problems of hinges, including accuracy, deformation, and residual stress. A femtosecond laser was used to release the anchor between the out-of-frame and the proof mass to protect the hinge. The isolation structure was designed to float both the DETFs and hinge to reduce the interference of external stress. Electrodes were deposited on the four surfaces of the vibrating beam in a three-segment configuration to excite the DETF into the antiphase in-plane vibration model. As a result, an accelerometer prototype is fabricated, and the performance characterization results exhibit the sensitivity and stability of 188.61 Hz/g and 7.81 ppm, respectively, and the bias instability (Allan deviation) of 1.26 μg, which proves the design rationality of laterally sensitive QVBA.

History and Evolution of the Tuning Fork.

This paper is a summary of the evolution of the tuning fork, a crucial part of the cranial nerves and auditory examination. The tuning fork is a two-pronged fork that resonates at a specific pitch when struck against a surface and has been proven to be incredibly useful in diagnosing and detecting hearing disorders. The tuning fork, an unassuming device in modern medicine, traces its origins back to an era when scientific understanding and medical diagnostics were in their nascent stages. Since its inception, this unpretentious instrument has played a pivotal role in the hands of healthcare practitioners, aiding in the diagnosis and assessment of various medical conditions. This paper embarks on a captivating journey through time to explore the origin, evolution, and significant milestones in the development of the tuning fork. From the first suggestion of differentiating hearing disorders to present-day tuning forks, this paper maps the different stages that the tuning fork has gone throughand how its use has changed over time. Along the way, we will discover how the tuning fork has harmonized with music, medicine, and various scientific pursuits, enriching our understanding of sound and resonance while leaving an indelible mark on the course of human history.Delving into the historical context of its creation, this review uncovers the ingenious minds that birthed this innovative device and the pivotal moments that brought it to the forefront of human endeavors.